1. [n]  the position of a player on a football team who is stationed behind the line of scrimmage
2. [n]  a support that you can lean against while sitting; "the back of the dental chair was adjustable"
3. [n]  the part of a garment that covers your back; "they pinned a `kick me' sign on his back"
4. [n]  the front and back covering of a book; "the book had a leather binding"
5. [n]  the side that goes last or is not normally seen; "he wrote the date on the back of the photograph"
6. [n]  the posterior part of a human (or animal) body from the neck to the end of the spine; "his back was nicely tanned"
7. [n]  the series of vertebrae forming the axis of the skeleton and protecting the spinal cord; "the fall broke his back"
8. [n]  the part of something that is furthest from the normal viewer; "he stood at the back of the stage"; "it was hidden in the rear of the store"
9. [n]  (football) a person who plays in the backfield
10. [adv]  in or to or toward a past time; "set the clocks back an hour"; "never look back"; "lovers of the past looking fondly backward"
11. [adv]  at or to or toward or the back or rear; "he moved back"; "tripped when he stepped backward"; "she looked rearward out the window of the car"
12. [adv]  in repayment or retaliation; "we paid back everything we had borrowed"; "he hit me and I hit him back"; "I was kept in after school for talking back to the teacher"
13. [adv]  in or to or toward a former location; "she went back to her parents' house"
14. [adv]  in or to or toward an original condition; "he went back to sleep"
15. [adv]  in answer; "he wrote back three days later"; "had little to say in reply to the questions"
16. [v]  shift to a counterclockwise direction; "the wind backed"
17. [v]  strengthen by providing with a back or backing
18. [v]  establish as valid or genuine; "Can you back up your claims?"
19. [v]  place a bet on; "Which horse are you backing?"; "I'm betting on the new horse"
20. [v]  travel backward; "back into the driveway"; "The car backed up and hit the tree"
21. [v]  cause to travel backward; "back the car into the parking spot"
22. [v]  support financial backing for; "back this enterprise"
23. [v]  be behind; approve of; "He plumped for the Labor Party"; "I backed Kennedy in 1960"
24. [v]  give support or one's blessing to; "I'll second that motion"; "I can't back this plan"; "endorse a new project"
25. [v]  be in back of; "My garage backs their yard"

BACK is a 4 letter word that starts with B.

1. \Back\, n. [F. bac: cf. Arm. bak tray, bowl.]
   1. A large shallow vat; a cistern, tub, or trough, used by
      brewers, distillers, dyers, picklers, gluemakers, and
      others, for mixing or cooling wort, holding water, hot
      glue, etc.
   {Hop back}, {Jack back}, the cistern which receives the
      infusion of malt and hops from the copper.
   {Wash back}, a vat in which distillers ferment the wort to
      form wash.
   {Water back}, a cistern to hold a supply of water; esp. a
      small cistern at the back of a stove, or a group of pipes
      set in the fire box of a stove or furnace, through which
      water circulates and is heated.
   2. A ferryboat. See {Bac}, 1.
   

2. \Back\, n. [As b[ae]c, bac; akin to Icel., Sw., & LG. bak,
   Dan. bag; cf. OHG. bahho ham, Skr. bhaj to turn, OSlav. b?g?
   flight. Cf. {Bacon}.]
   1. In human beings, the hinder part of the body, extending
      from the neck to the end of the spine; in other animals,
      that part of the body which corresponds most nearly to
      such part of a human being; as, the back of a horse, fish,
      or lobster.
   2. An extended upper part, as of a mountain or ridge.
            [The mountains] their broad bare backs upheave Into
            the clouds.                           --Milton.
   3. The outward or upper part of a thing, as opposed to the
      inner or lower part; as, the back of the hand, the back of
      the foot, the back of a hand rail.
            Methought Love pitying me, when he saw this, Gave me
            your hands, the backs and palms to kiss. --Donne.
   4. The part opposed to the front; the hinder or rear part of
      a thing; as, the back of a book; the back of an army; the
      back of a chimney.
   5. The part opposite to, or most remote from, that which
      fronts the speaker or actor; or the part out of sight, or
      not generally seen; as, the back of an island, of a hill,
      or of a village.
   6. The part of a cutting tool on the opposite side from its
      edge; as, the back of a knife, or of a saw.
   7. A support or resource in reserve.
            This project Should have a back or second, that
            might hold, If this should blast in proof. --Shak.
   8. (Naut.) The keel and keelson of a ship.
   9. (Mining) The upper part of a lode, or the roof of a
      horizontal underground passage.
   10. A garment for the back; hence, clothing.
             A bak to walken inne by daylight.    --Chaucer.
   {Behind one's back}, when one is absent; without one's
      knowledge; as, to ridicule a person behind his back.
   {Full back}, {Half back}, {Quarter back} (Football), players
      stationed behind those in the front line.
   {To be or lie on one's back}, to be helpless.
   {To put}, {or get}, {one's back up}, to assume an attitude of
      obstinate resistance (from the action of a cat when
      attacked.). [Colloq.]
   {To see the back of}, to get rid of.
   {To turn the back}, to go away; to flee.
   {To turn the back on one}, to forsake or neglect him.
   

3. \Back\, a.
   1. Being at the back or in the rear; distant; remote; as, the
      back door; back settlements.
   2. Being in arrear; overdue; as, back rent.
   3. Moving or operating backward; as, back action.
   {Back charges}, charges brought forward after an account has
      been made up.
   {Back filling} (Arch.), the mass of materials used in filling
      up the space between two walls, or between the inner and
      outer faces of a wall, or upon the haunches of an arch or
      vault.
   {Back pressure}. (Steam Engine) See under {Pressure}.
   {Back rest}, a guide attached to the slide rest of a lathe,
      and placed in contact with the work, to steady it in
      turning.
   {Back slang}, a kind of slang in which every word is written
      or pronounced backwards; as, nam for man.
   {Back stairs}, stairs in the back part of a house; private
      stairs. Also used adjectively. See {Back stairs},
      {Backstairs}, and {Backstair}, in the Vocabulary.
   {Back step} (Mil.), the retrograde movement of a man or body
      of men, without changing front.
   {Back stream}, a current running against the main current of
      a stream; an eddy.
   {To take the back track}, to retrace one's steps; to retreat.
      [Colloq.]
   

4. \Back\, v. i. [imp. & p. p. {Backed}; p. pr. & vb. n.
   {Backing}.]
   1. To get upon the back of; to mount.
            I will back him [a horse] straight.   --Shak.
   2. To place or seat upon the back. [R.]
            Great Jupiter, upon his eagle backed, Appeared to
            me.                                   --Shak.
   3. To drive or force backward; to cause to retreat or recede;
      as, to back oxen.
   4. To make a back for; to furnish with a back; as, to back
      books.
   5. To adjoin behind; to be at the back of.
            A garden . . . with a vineyard backed. --Shak.
            The chalk cliffs which back the beach. --Huxley.
   6. To write upon the back of; as, to back a letter; to
      indorse; as, to back a note or legal document.
   7. To support; to maintain; to second or strengthen by aid or
      influence; as, to back a friend. ``Parliament would be
      backed by the people.'' --Macaulay.
            Have still found it necessary to back and fortify
            their laws with rewards and punishments. --South.
            The mate backed the captain manfully. --Blackw. Mag.
   8. To bet on the success of; -- as, to back a race horse.
   {To back an anchor} (Naut.), to lay down a small anchor ahead
      of a large one, the cable of the small one being fastened
      to the crown of the large one.
   {To back the field}, in horse racing, to bet against a
      particular horse or horses, that some one of all the other
      horses, collectively designated ``the field'', will win.
   {To back the oars}, to row backward with the oars.
   {To back a rope}, to put on a preventer.
   {To back the sails}, to arrange them so as to cause the ship
      to move astern.
   {To back up}, to support; to sustain; as, to back up one's
      friends.
   {To back a warrant} (Law), is for a justice of the peace, in
      the county where the warrant is to be executed, to sign or
      indorse a warrant, issued in another county, to apprehend
      an offender.
   {To back water} (Naut.), to reverse the action of the oars,
      paddles, or propeller, so as to force the boat or ship
      backward.
   

5. \Back\, v. i.
   1. To move or go backward; as, the horse refuses to back.
   2. (Naut.) To change from one quarter to another by a course
      opposite to that of the sun; -- used of the wind.
   3. (Sporting) To stand still behind another dog which has
      pointed; -- said of a dog. [Eng.]
   {To back and fill}, to manage the sails of a ship so that the
      wind strikes them alternately in front and behind, in
      order to keep the ship in the middle of a river or channel
      while the current or tide carries the vessel against the
      wind. Hence: (Fig.) To take opposite positions
      alternately; to assert and deny. [Colloq.]
   {To back out}, {To back down}, to retreat or withdraw from a
      promise, engagement, or contest; to recede. [Colloq.]
            Cleon at first . . . was willing to go; but, finding
            that he [Nicias] was in earnest, he tried to back
            out.                                  --Jowett
                                                  (Thucyd. )
   

6. \Back\, adv. [Shortened from aback.]
   1. In, to, or toward, the rear; as, to stand back; to step
      back.
   2. To the place from which one came; to the place or person
      from which something is taken or derived; as, to go back
      for something left behind; to go back to one's native
      place; to put a book back after reading it.
   3. To a former state, condition, or station; as, to go back
      to private life; to go back to barbarism.
   4. (Of time) In times past; ago. ``Sixty or seventy years
      back.'' --Gladstone.
   5. Away from contact; by reverse movement.
            The angel of the Lord . . . came, and rolled back
            the stone from the door.              --Matt. xxvii.
                                                  2.
   6. In concealment or reserve; in one's own possession; as, to
      keep back the truth; to keep back part of the money due to
      another.
   7. In a state of restraint or hindrance.
            The Lord hath kept thee back from honor. --Numb.
                                                  xxiv. 11.
   8. In return, repayment, or requital.
            What have I to give you back!         --Shak.
   9. In withdrawal from a statement, promise, or undertaking;
      as, he took back0 the offensive words.
   10. In arrear; as, to be back in one's rent. [Colloq.]
   {Back and forth}, backwards and forwards; to and fro.
   {To go back on}, to turn back from; to abandon; to betray;
      as, to go back on a friend; to go back on one's
      professions. [Colloq.]